Fusarium graminearum forms mycotoxin producing infection structures on wheat

Area of Science:

• Plant pathology
• Mycology
• Molecular genetics

Background:

• Fusarium graminearum causes Fusarium head blight (FHB) in cereals worldwide.
• Initial infection stages and the role of mycotoxins in FHB are poorly understood.
• Investigating fungal infection strategies on wheat floral organs is crucial.

Purpose of the Study:

• To investigate the infection strategy of Fusarium graminearum on wheat floral organs.
• To visualize trichothecene induction during initial infection stages.
• To elucidate the role of trichothecene production in FHB pathogenesis.

Main Methods:

• Real-time imaging of F. graminearum using dsRed and GFP reporter genes (TRI5prom::GFP).
• Bioimaging and electron microscopy to identify and characterize infection structures.
• Utilizing a ΔTRI5-GFP mutant to assess the necessity of trichothecene production.

Main Results:

• F. graminearum forms specialized infection structures, including foot structures and compound appressoria, on various wheat floral organs.
• Trichothecene biosynthesis is specifically induced within these infection structures.
• A mutant lacking TRI5 (ΔTRI5-GFP) developed similar infection structures and symptoms as the wild type.

Conclusions:

• F. graminearum exhibits a complex infection strategy on wheat florets, involving specialized structures.
• Trichothecene biosynthesis is induced during infection but is not required for infection structure development or primary symptom formation.
• The role of mycotoxins in the initial stages of FHB may be less critical than previously assumed.